摘要目的 观察DNA甲基转移酶1(DNMT1)基因沉默后对人胰腺癌PaTu8988细胞的DNMT活性及hMLH-1基因CpG岛DNA甲基化状态的影响.方法 由美国Ambion公司设计合成DNMT1siRNA和阴性对照siRNA,分别用15、30 nmol/L的浓度转染胰腺癌PaTu8988细胞,以未转染组细胞作为对照.应用实时PCR和蛋白质印迹法检测DNMT1 mRNA和蛋白的表达；用DNMT活性检测试剂盒检测其活性；用亚硫酸氢盐测序PCR(BSP)法检测hMLH-1基因CpG岛的甲基化状态；实时PCR法检测hMLH-1 mRNA的表达.结果 转染48 h后,DNMT1 siRNA15、30 nmol/L组细胞DNMT1 mRNA表达量分别为0.573±0.026和0.143±0.044,显著低于对照组的1.020±0.217及阴性siRNA 15、30 nmol/L组的0.900±0.475和0.938±0.327(P值均＜0.05)；DNMT1 siRNA组的DNMT1蛋白表达亦低于对照组和阴性siRNA组.DNMT1 siRNA15、30 nmol/L组细胞DNMT活性分别为0.364±0.124和0.250±0.072,明显低于对照组的0.931±0.065及阴性siRNA 15、30 nmol/L组的0.665±0.055和0.472±0.040.DNMT活性与DNMT1 mRNA表达呈正相关(r=0.69,P＜0.01).DNMT1 RNA干扰后导致hMLH-1基因CpG位点的8个甲基化减少到1个甲基化.结论 DNMT1 siRNA能特异性抑制胰腺癌PaTu8988细胞DNMT1基因的表达,明显抑制DNMT的活性,并引起hMLH-1基因CpG岛去甲基化.

abstractsObjective To assess the effects of DNA methyhransferase 1 ( DNMT1 ) gene silencing on DNMTs activity and methylated CpG sites of hMLH-1 in pancreatic cancer cell line PaTu8988.Methods DNMT1 siRNA and negative control siRNA was constructed by Ambion Company of United States.Then they were transfected into pancreatic cancer cell line PaTu8988 at the concentrations of 15,30 nmol/L,and the cells without transfection was used as the control group.Real-time PCR and Western blotting were applied to detect the DNMT1 mRNA and protein expression,and DNMTs activity was detected by using DNMTs activity assay kit.Change of methylation of CpG island of hMLH-1 was detected by bisulfite sequencing PCR (BSP).The expression of hMLH-1 mRNA was detected by Real-time PCR.Results At 48 h after transfection,Realtime RT-PCR analysis showed that the levels of DNMT1 mRNA in DNMT1 siRNA group ( 15 nmol/L) and DNMT 1 siRNA group (30 nmol/L) were 0.573 ± 0.026 and 0.143 ± 0.044,which were significantly lower than those in control group 1.020 ±0.217 and negative siRNA 15 nmol/L group 0.900 ±0.475,and negative siRNA 30 nmol/L group 0.938 ± 0.327 (P ＜0.05 ).Western blotting analysis showed that the level of DNMT1 protein of DNMT1 siRNA group was also lower than those of negative siRNA and control groups.DNMT activity in DNMT1 siRNA15,30 nmol/L groups was 0.364 ± 0.124and 0.250 ± 0.072,which were significantly lower than those in control group 0.931 ± 0.065and negative siRNA group 0.665 ± 0.055 and 0.472 ± 0.040.DNMT activity was positively correlated with DNMT1 mRNA expression ( r =0.69,P ＜ 0.01 ).DNMT1 RNA interference decreased 8 methylated CpG sites of hMLH-1 to 1 site.Concluslons DNMT1siRNA can specifically inhibit the expression of DNMT1 gene of PaTu8988 and DNMT activity,and can decrease methylated CpG sites of hMLH-1 gene.